Hydraulically operated machine tool



ug. 31p 1937. W, H WOOD .2,091,425

HYDRAULICALLY OPERATED MACHINE TOOL IFiled Dec. 15, 1932 5 Sheets-Sheet 1 25 254 24o 185' H4- 154 |13 6,190 la? 153 154. ,93

`v y 163 155 164 l v [66 [6l z qs 1 9]|/6o a o J l t les '591571 s 156 15e v /olaz [56 y 4 les@ ""267 "l "7 4 WALLACE H. Woon WWA/E565 115 c? 244 T n M *AW VW www ug. 31, 1937, W H WOOD 2,091,425

HYDRAULICALLY OPERATED MACHINE TOOL Filed Dec. 15, 1932 5 Sheets-Sheet 2 105' 104 loe 82 gwoentoz WA LLAcE H. Woon Aug. 3i, E937. w. H. woon 2,09L425 HYDRAULICALLY PERATED MACHINE TOOL Filed Deo. l5, 1932 3 Sheets-Sheet 3 WALLACE H. Woon WWA/56656 Patented Aug.k 31,4 1937 HYDRAULICALLY OPERATED MACHINE' TOOL Wallace H. Wood, Worcester, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application December 15, 1932, Serial No. 647,311 12 claims. (o1. 51-232.)

This invention relatesto hydraulically operated machine tools, such as grinding machines, and more particularly to a table traversing mechanism therefor.

Heretofore various machine tools have been provided With fluid pressure actuated table traverse mechanisms adapted to reciprocate a work piece while in engagement with a cutting tool and to thereby cause a continued rapid cutting operation upon the work. These prior machines have, due to their constructions, often been subjected to shocks and jars at time of reversal and have usually employed an additional separate table traverse mechanism which could be manually actuated by means of a hand wheel or other suitable device. In these prior constructions, it has .been found impractical to change from the automatic fluid pressure table traverse to the manually operated table traverse without rst disengaging the fluid pressure mechanism and removing the fluid pressure from the table operating device. Such a construction'has tended to cause air pockets to form in the uid pressure system and has often resulted in uneven and inaccurate table reciprocation, thereby spoiling the work which must be smoothly reciprocated during the cutting operation thereon. 1

It is accordingly the primary object of my in vention to provide an automatically operated table reciprocating mechanism wherein the table may be smoothly brought to a stop and started again at the time of its reversal without any shocks', jars or uneven table movement.

A further object of this invention is to provide a iluid pressure actuated table traverse mechanism for machine tools, wherein the table may be stopped at any time during its reciprocation and manually traversed without disconnecting the fluid pressure system from the table actuating 40 mechanism.

In prior hydraulically operated table traverse mechanisms, it has been the usual practice to provide a relatively reciprocable vpiston and cylinder device connected to a reversing valve which 4,-, stops thel table movement at time of reversal by pocketing fluid in the cylinder on opposite sides of the piston under a zero pressure. Since the iuid is pocketd, there can be no relative piston and cylinder movement, and as a consequence no 50 table traverse at this time. When the reversing valve in such a construction is shifted to a table traverse position, one end of the cylinder is suddenly opened to full fluid pressure while the other end of the cylinder is opened to the exhaust.

55 This sudden increase in pressure usually causes to a position to by-pass fluid;

the table movement to start with uneven shocks and jars.

It is, therefore, a still further object of this invention to provide a machine tool having a fluid pressure actuated table reciprocating mech- 5 anism wherein the table may be caused to evenly start traversing due to a reduction of one of two balanced iluid pressures within the table reciprocating mechanism.

Other objects will be apparent from the foregoing disclosure. One embodiment of this invention has .been illustrated in the accompanying drawings, in which like reference numerals indicate like parts: v l

Fig. 1 is a front elevation of a grinding machine embodying this invention:

*Fig. 2 is a diagrammatic view of the valve mechanism showing a table dog contacting with -the pilot valve lever preparatory to stopping the been automatically stopped; 5'

Fig. 4 is a diagrammatic view showing the relative positions of the valve mechanism and table when table reversal is completed and the table is just starting to move toward the left;

Fig. 5 is a diagrammatic view showing the positions of the valve mechanism and table when the table has completed its movement towards the left and just prior to its reversal;

Fig. 6 is a diagrammatic view showing the piston locations of the by-pass valve when shifted l Fig. 'l is a sectional view taken approximately on the line 1-1 of Fig. 1; v Fig. 8 is a fragmentary view showing the relative positions of the control levers and pilot valve while the table is moving towards the left;

Fig. 9 is a fragmentaryview taken along the line 9-9 of Fig. 8;

Fig. 10 is a fragmentary view showing the speed control valve; and

Fig. 11 is a fragmentary view showing the mechanism employed to locate the icy-pass valve 'in either operative position.

The speclc embodiment of this invention, as illustrated in the drawings,v comprises a grind- 50 ing machine having a iiuid pressure operated table reciprocating mechanism so arranged that the tablemay be traversed in both directions at any desired rate of speed and caused. to dwell at the termination of each. reciprocatory stroke for,l

a predetermined but variable period of time. The table reciprocating mechanism includes a table actuating motor, a reversing valve, a pilot valve and a by-pass valve. Dogs adjustably positioned on the table serve to shift the reversing valve to a neutral position which rst stops the table traverse at each end of a predetermined reciprocatory stroke and then applies balanced fluid pressures within the table actuating motor. At the same-time that the reversing valve is shifted to a neutral position, the pivot valve is automatically shifted and admits a controlled amount of fluid under pressure into one end of the reversing valve at a regulated rate, thereby Serving to shift the reversing valve into an operative position which gradually unbalances the fluid pressures in the table motor and starts the table evenly traversing without shocks or jars in an opposite direction after a predetermined but adjustable dwell period. A manually operable by-pass valve is also provided whereby fluid may be passed around the table actuating mechanism at'any time and stop the movement of the table under the influence of fluid pressure whenever desired without disconnecting the iiuid pressure mechanism from the table. When this by-pass valve is in an operative position, the table may be traversed manually by any suitable mechanism, irrespective of the positions of other valves in the fluid pressure system.

As illustrated in the drawings, this machine comprises a base supporting a rotatable grinding wheel 2| on a wheel slide 22, which is arranged for movement transversely of the base. The base is also provided with a work supporting table slidably mounted for longitudinal movement thereon. The work table 25 is provided with a headstock 21 and a footstock 28 which may be adjustably positioned in any well-known manner to rotatably support a work piece upon the respective centers 39 and 3|. The work may be rotated by any convenient means which in the present instance comprises a motor 32 mounted on the headstock 21 and connected to rotate a face plate 33 having a work driving dog 34 secured thereto.

' The table 25 may be reciprocated by a fluid pressure actuated device, which is so arranged that the table is caused to dwell in its movement for short, predetermined but variable periods at both ends of the table reciprocation. This mechanism may comprise a relatively reciprocable, fluid pressure actuated piston and cylinder connected between the base 20 and the table 25 to control the movement of the table. As illustrated in the drawings, the cylinder 31 is secured to the under side of the table 25 and arranged for movement therewith. A piston 39 having two opposed faces of equal pressure areas is slidably mounted within the cylinder 31 and maintained in a fixed position relative to the base by means of two connecting rods 49 and 4| secured thereto. The piston 39 .is preferably formed as two separate spaced pistons which are rigidly connected to the ends of hollow piston rods 40 and 4| respectively. These connecting rods are slidable through the cylinder heads 43 and 44 xed to the ends of cylinder 31 and are secured at their outer ends to the brackets 45 and 46 which are fastened to the machine base 20. The brackets 45 and 46 are provided with chambers 48 and 49 arranged to communicate with passages 5| and 52 within the piston rods 49 and 4| respectively. The hollow rods 40 and 4| are further provided with ports 53 and 54 00mmunicating with the passages 5| and 52 respectively, which are located adjacent to the ends of the piston 39, whereby fluid may enter or leave each end of cylinder 31. It will thus be apparent that fluid under pressure lmay communicate with either chamber 48 or 49 from any suitable source to cause a controlled table movement. For example, fluid under pressure may enter chamber 48, pass through passage 5| and port 53 into the left-hand end of cylinder 31, causing a'movement of the table toward the left. At this time, fluid may flow from the righthand end of the cylinder 31 out through port 54, passage 52 .and chamber 49 to a suitable exhaust. The ports 53 and 54 are elongated and V-shaped adjacent to the piston 39. This construction prevents a shock stop of the table if. the cylinder is permitted to travel its greatest possible stroke, since the exhaust port 53 or 54 through which fluid flows back into the supply tank may be gradually throttled by the cylinder head partially covering said port.

To reverse the direction of the table movement, the fluid pressure system is provided with a reversing valve 6|) connected to both ends of the cylinder 31 through the respective chambers 48 and 49. A pilot valve 6| is further provided and arranged to shift the reversing valve 6D and thereby change the direction of fluid flow to the chambers 48 and 49 and cylinder 31. In the base of the machine, a fluid supply reservoir 63 is provided, and fluid is pumped therefrom under pressure by a suitable pump, such as a gear pump 64. Fluid under pressure flows from the pump 64 through pipes 65 and 66 which communicate respectively withA port 61 of the pilot valve 6| and ports 68 and 69 of the reversing valve.

The reversing valve is provided with a-valve stem 10 having pistons 1|, 12, 13, and 14 mounted thereon and slidable within a cylinder sleeve 15 which contains the valve ports 68 and 69 and is xedly positioned between cylinder heads 16 and 11 of thev reversing valve. The valve ports 68 and 69 connect with chambers 80 and 9| which lie respectively between valve pistons 1| and 12, and 13 and 14. Sleeve 15 is also provided with ports 82 and 83, communicating respectively through pipes 85 and 86 with chambers 48 and 49 and'cylinder 31. further provided with a port which is in continuous communication with chamber 9| between the valve pistons 12 and 13 and also with a pipe 92 which may connect through a suitable exhaust system with the supply reservoir 63.

Sleeve 15 is I,

Thereversing valve stem 1D and pistons 1|,

12, 13, and 14 thereon may be shifted to change the direction of table travel by means of suitable mechanism. In the preferred embodiment of this invention, the movement' of the table serves to actuate the valve stem 10 and shift the reversing valve to a neutral position when the table has reached a predetermined position, thereby automatically stopping table'movement.

The pilot valve 5| is also actuated by the table 1 thereto, so that any angular movement thereof will cause a corresponding angular movement of depending lever 91. The upper end of the lever IOI is provided with a pin |04 arranged to be engaged by adjustable dogs |05 and |06 depending from the' table and adjustably positioned within a T-slot |01 cut in the forward side of the table 25.

During the normal travel of thetable, the pilot l0 valve is maintained lin a neutral position, as shown in Fig. 2; that is, with the pilot valve pistons ||0 and ||I positioned to cover the ports I I2 and II3 respectively, which lie within a valve sleeve II4 and communicate with the reversing valve. When the pilot valve is in this neutral position, fluid under pressure from the pump 64 may enter a chamber ||5 between pistons ||0 and I I I, but it cannot iiow from the pilot valve` to the reversing valve, since ports ||2 and ||3 are closed, as shown in Fig. 2.

Assuming the'table to be traversing toward the right, as shown in Fig. 2, the valve pistons will remain in the position there shown until the table dog |05 engages the pin |04 and rocks the lever ll'towards the right to the position shown in Fig. 3. This movement shifts the valve stem 95 so that pilot valve pistons |I0, ||I, and I |1 move towards the left and assume the positions illustrated in Fig. 3. Movement of the pilot valve pistons to these positions opens the port I|2 to admit fluid under pressure fromy chamber |I5 through port ||2, pipes |20 and |22 into the port I 23 and chamber |25 at the left-hand end of the reversing valve 60 between piston 1I and cylinder head 16. This permits the fluid pressure within the system`to pass back of the reversing valve piston 1| on valve stem 10 and shift the reversing valve pistons towards the right to the position shown in Fig. 4, causing a reversal of the table movement.

One feature of this invention involves provisions whereby the reversing valve may be automatically shifted to a neutral position by the table itself to stop the table movement when it has reached a predetermined position, and a definite period of dwell may also be provided at each end of the table reciprocation. To accomplish this, a suitable lever mechanism-is so arranged that it will be actuated in timed relation with the lever 91 which controls the movement of the pilot valve 6I. This may comprise a manually operable lever |30 fixed to the forward end of a shaft |3| which is journaled within sleeve 98, as shown in Fig. '7. 'I'he other end of shaft |3| is provided With a lever I 33 afxed thereto and depending therefrom, said lever being connected to operate the reversing valve stem 10 through an adjustable connecting link |34. As illustrated in Figs. '1, 8, and'9, the levers 91 and |33 are connected through a lost motion linkage so that when one of the table dogs moves lc'ver I0| to such a position as to open the pilot valve, the reversing valve is automatically shifted to a neutral position to stop the table movement. The upper vend of lever 91 is provided with two outwardly projecting portions or fingers |40 and |4| which are respectively engageable with two projecting arms |42 and |43 of avbell crank |45 journaled on a pin |46 supported on the machine base. The arms |4I and |42 are provided with studs |41 and |48 screwed therein and locked in position by lock nuts so thatv the amount of lost motion between the respective arms may be regulated.- `Bell crank |45 is further provided with a depending arm |53 which is connected to move the lever |33 through a cooperating link |54 /pivotally connected between said depending arm and lever.

As the table traverses toward the right, as y shown in Fig. 2', the dog |05 engages lever |0I, which is normally maintained in a. vertical position, yand moves it towards the right to the position shown. in Fig. 3. 'I'hls movement of lever |0| rocks lever 91 through a corresponding angle and thereby lifts the projecting nger I4| which after the required extent of lost motion engages bell crank arm |43, thereby rocking bell crank |45 and moving the reverse valve to a neutral position (Fig. 3) dthrough depending'arm |53, link |54 and lever |33.

Tol prevent possible injury to the machine caused by an incorrect adjustment of the lost motion device, a compensating mechanism is provided, as shown in Fig. 8. This may comprise a double head yoke member |55 pivotally connected by pins |56 to the lower end of lever 91 for swinging movementA therewith and slidably mounted upon sleeves |51 and |58 which are slidably mounted upon a rod |59 passing through the yoke member and connecting with piston rod 95 through an adjustable link I 60. The ends of member are provided with reduced portions |6| and |62, which are slidably journaled upon the respective sleeves 51 and |58 and engageable with heads |63 and I 64 on the'inner ends of said sleeves. A coil spring |65 surrounding the rod |59 is compressed between the heads |63 and |64 and normally holds said heads in engagement with the respective reduced portions |6| and |62 of member |55. The maximum extent of movement of sleeves |51 and |58 may be limited by collars I6|i.and |61 avxed to the rod |59. The Vcollars |66 and- |61 are so located with relation toeach other that the spring I 65 is under sufficient compression to normally transmit the movement of lever 91 directly to rod |59 without ,further compression of said spring and thereby cause a corresponding movc" To prevent shocks in stopping the table when it is being traversedin either direction by fluid pressure, the reversing valve ports 82 and 83 communicating with the opposite ends of the table cylinder have been so located that as the lever |33 moves the reversing valve pistons into a neutral position, one of said ports 82 or 83 is momentarily closed by one of the valve pistons, thereby pocketing uid in one end of the table cylinder 31 and stopping the table traverse. Immediately thereafter, when the pistons reach their neutral position, as shown in dotted lines in Fig. 2, the pistons 12 and 13 are so positioned that they do not completely cover the ports 82 and 83, thereby directing full fluid pressure through said ports into both ends of the table cylinder. The opposite faces of piston 39'..within the table cylinder have equal areas. Hence, it will be appreciated that when iiuid is pocketed in one endv of cylinder 31., and the other end of the cylinder is still open to full fluid pressure, the pocketed fluid will be compressed until the pressures against the opposed piston faces of piston 39 will be balanced, serving to bring the table to a cushioned 'positive stop. Continued movement of the reversing valve pistons to a. neutral position, as shown by the dotted line piston positions in Fig. 2, does not alter the conditions within the cylinder 31,'but transfers full iluid pressure from the pump 64 to both ends of the cylinder 31, maintaining the balanced pressures against the opposed faces of piston 39 even when there is a leakage of fluid through the piston rod bearings in cylinder heads 43 and 44. Excess fluid pressure will not tend to build up with the iiuid system at this time, since it may be relieved by any well-known type of relief valve |61 and passed back into the supply tank 63 through a pipe |68. A table traverse control, as provided by this invention, has been found to be very smooth, accurate andpositive in its operation. In repeated tests of this machine, the table traverse has been brought to a smooth positive stop with variations of not over two ten-thousandths of an inch, thereby providing an automatically controlled table traverse mechanism which is admirably suited to nishing a work surface close to a. shoulder.

In order that the period of table dwell may be varied at the right-hand end of the table stroke, a suitable valve |69 is interposed between the pipes |20 and |22 which connect the pilot valve6| to the rreverse valve 60. This dwell control valve may piston |13 is slidably mounted within cylinder- |10 and arranged to vary the extent of closure of port |1| by regulated -amounts controlled by a manually operable knob |14 projecting out through the front of the machine. The knob |14 is connected to the piston |13 by means. of a rod r|15 having an enlarged portion |16 threaded into a bearing member |11 secured to the outer end of the valve casing. A spring |18 is provided to prevent the knob from being turned too easily. It will thus be seen that by turning the knob |14, the rate of iiow of uid from the pilot valve to the reversing valve may beaccurately regulated, and the time required to shift the reversing valve from a neutral position (Fig. 3) to an operative vreverse position as shown in Fig. 4 may be controlled, thereby providing any desired period of dwell. For convenience of the operator, the knob |14 may be provided with graduations |19 which may be aligned with an index point on the base',

by a reduction of the fluid pressure at one end of the table traverse cylinder. Since the full operating pressure of the iiuid pressure system is maintained in a balanced relation against the opposed equal area faces of piston 89 when the-reversing traverse mechanisms.

After reversal of the table has taken place, the pilot valve stem 95 is automatically returned to aneutral position, wherein the ports ||2 and ||3 are both covered by pistons and I|| respectively, as shown in Fig. 2. This is accomplished by means of a coil spring |80 interposed between two collars |8| and |82 which are slidably mounted on valve stem 95 and respectively engageable with collars |83 and |84 afxed to said valve stem, as shown in Figs. 2 and 8. When the pilot valve is in a neutral position, the collars I8| and |82 engage shoulders on the pilot valve head |85 and the end of the valve sleeve |4 within the valve casing 6|, thereby limiting further movement of collars |8I and |82 against the shaft collars |83 and |84. The pilot valve pistons remain in the positions shown in Fig. 4 until the table moves in the reverse direction, towards the left. As soon as the table starts moving toward the left, the table dog withdraws from the pin |04, and the released pressure of spring |80 acts against collars' |83 and |84 to return the valve stem 95 and pistons thereon to a neutral position, as illustrated in Fig. 2.

In order to give suiiicient time for shifting the reversing valve 60, the return movement of the pilot valve stem4 95 and pistons thereon to a neutral position is retarded so that port 82 of the reversing valve 60 is completely opened before the pilot valve is returned to a neutral position. To accomplish this, pilot valve head |86 at the right-hand end of the pilot valve is provided with a chamber |81 communicating with a chamber |89 in the pilot valve between piston ||1 and valve head |86 by means of a small port |90. Chamber |81 may be supplied with fluid from any suitable source, as by a pipe |9| and valve |92 connected to the iiuid pressure system. It will thus be noted that when the pilot valve is shifted, chamber |89 will serve as a dash pot, and the rate of return movement of the pilot waive toa neutral position will be controlled by the rate of fluid ow through port |90.

. During the movement of 4the table toward the y left, as indicated in Fig. 4, uid under pressure passes from pump 64, through pipes 65 and 66, into the reversing valve through port 68, chamber 80, and therefrom through port 82, pipe 85, chamber- -48, passage .5|, and into the left-hand end of table cylinder 31 through port 53. At this time, iiuid may exhaust from the right-hand end of cylinder 31 through port 54, passage 52, chamber 49, pipe 86, into reverse valve chamber 9|, l

through port 83, and then out through port 90, pipe 92, through a by-passvalve |95, pipe |96, into a chamber |98 in a speed control valve |99. 'I'his speed control valve, as illustrated, is of the balanced piston type and is provided with a piston 200, arrangedto be moved within the valve |99 and thereby control the closure of an elongated V-shaped port 202 (Fig. communicating through pipes 203 and 204 with the iiuid supply tank 63.

The closure of V-shaped port 202 may be manually controlled from the front of the machine to regulate the rate of reciprocation of table 25. To accomplish this, the piston 200 is surrounded by a sleeve member 206 provided with a reduced portion 201, projecting through the front of the machine and having a control knob 208 secured thereto, as shown in Fig. 10. Sleeve 206 is provided with a helical slot 2|0, and the valve body |99 is provided with a longitudinal slot 2li cut axially of said piston and sleeve. A pin 2|2 pro- 4jects radially from piston 200 and passes through both of said slots. It will thus be apparent that any angular movement of knob 208 will serve to rotate sleeve 206 andcause pin 2 I 2 to move longitudinally of slot 2| I, thereby moving piston 200 to close or openthe V-shaped port 202 and control the iluid ow therethrough in its return to tank 63. For convenience of adjustment, the knob 208 may be provided with a scale of graduations aligned with an index mark on the machine.

'Ihe speed control valve may also be so adjusted that the rotationy of knob 208 may not reduce table movement below a preadjusted minimum table speed. To accomplish this, piston 200 is provided with a piston rod engageable with the arm 2|4 of a bell crank lever 2|5 pivoted on valve casing |99. A depending arm 2|1 of bell crank 2 I5 is engaged by a rod 220 screw threaded within the base and provided with a head 22| projecting through the front of the machine. A spring 222 serves to maintain bell crank arm 2|1 and rod 220 in engagement. It will be apparent that by turning screw head 22 I, the position of bell crank arm 2|4 is regulated and knobl 208 cannot move piston 200 and the piston rod beyond this locating position, thereby limiting the extent of closure of port 202. 'Ihis feature is particularly useful,

since it is often desired to rapidly traverse the table and shortly-thereafter to reduce the table movement to a slow preadjusted speed.

Movement of the table toward the left, as indicated in Fig. 4, continues until the table dog |06 engages pin |04 and rocks lever |0| towards the left-hand position, as shown in Fig. 5. When lever |0| is shifted towards the left, as shown in Fig. 5, lever 91 is moved through a corresponding angle and finger |40 `is moved downward, engaging bell crank a-rm |42 after the required extent of lost motion. Movement of bell crank arm |42 is transmitted throughthe depending arm |53 and link |54 to shift lever |33 to such a position as to bring the reverse valve to a neutral position, as shown in Fig. 3, to stop the table move-l ends of i the table cylinder. Movement of lever |0| to this left-hand position acts through sleeve 98 and lever 91 to shift the pilot valve from a neutral position (Fig. 2`) to the position shown in Fig.5, wherein fluid may flow under pressure from pump 64 through pipe 65 and port 61 into chamber ||5 and out through port ||3, through pipe 225 and into a dwell control valve 221 arranged to control the dwell at the left-hand end of the table stroke, and which is of the same construction as dwell control valve |69. Dwell control valve 221 may be regulated by a knob 228 on the front of the machine. Fluid flows from the dwell control valve 221, out through pipes 230 and 23| and through a port 234 into a chamber 235 in the right-hand end of reverse valve between piston 14 and valve head 11, acting to shift4 228 in an identical manner to the adjustment of dwell control valve |69.

In order to give ample time for shifting the reversing valve 60, the return movement of the pilot valve 6| from the position shown in Fig. 5 to the neutral position, as shown in Fig. 2, which is caused by spring |80, is delayed by the flow of uid from ,the dash pot chamber |81 through port into chamber |89.

. Upon-completion of the movement of the reversing valve pistons to the position as shown in Fig. 2, the table movement is started toward the right and uid may now flow under pressure from pump 64 through pipes 65 and 66, and through port 69 into reverse valve chamber 8|, from which fluid flow will be directed through port 83, pipe 86, chamber 49, passage 52 and port 54 into the right-hand end of cylinder 31, causing table movement toward the right. At this time, fluid may exhaust from table cylinder 31 out through port 53, passage 5|, chamber 48, pipe 85 and port 82 into the reverse valve chamber 9|, from which uid will ilow through port 90, pipe 92, by-pass valve |95, pipe |96, speed control valve |99, and pipes 203 and 204 back to supply tank 63.-

When the reversing valve isshifted toward the right, as occurs during the reversal of the tabl'e at the termination of its stroke toward the right, fluid within reverse valve chamber 235 is free to flow into the exhaust system. This is accomplished by a pilot valve chamber 240 between the pilot valve pistons and 1, opening communication between a port 24| communicating with the exhaust system through a pipe 242, and a port 244 connected with a pipe 245 joining pipe 23|, said communication being effected only when the pilot valve pistons are shifted to a position to cause the reverse valve to move toward the right, as shown in Fig. 3.. It will be apparent that the exhaust uid is free to ilow at this time from chamber 235 through pipes 23| and 245 and port 244 into pilot valve chamber 240 and then back to the supply tank through port 24| and pipes 242, 203 and 204.

When the reversing valve 60 is shifted toward the left, as occurs during reversal of the table at thetermination of its stroke toward the left, fluid within reverse valve chamber |25 is free to r flow into the exhaust system. 'I'his is accomment and apply balanced uid pressures to both .255 joining pipe |22, said communication being eilected only'when -the pilot valve is shifted to a position to move the reverse valve toward the left, as shown in Fig. 5.

It is often desirable to stop the reciprocation of the table and traverse it by a manually oper-A ated mechanism. To accomplish this, a by-pass valve has been provided whereby fluid may be by-passed from one end of cylinder 31 to the other at any time without disconnecting the fluid pressure system from the table or stopping the pump 64. The by-pass .valve |95 is provided with a cylinder 215 having pistons 216, 211 and 218 slidably mounted therein and connected by a piston rod 219 which may be axially moved to various positions by any convenient means, such as a lever 282 pivotally mounted on a pin 283and provided with a depending portion 284 engagingrod 219. During the normal operation of the machine when the table 21 is being reciprocated by uid pressure, a chamber 285 in the by-pass ,valve located between pistons 216 and 211 offers communication between exhaust pipes 92 and |96, whereby uid may exhaust through speed control valve |99, pipes 203 and 204 back to the supply tank 63. The valve cylinder 215 is further provided with two ports 286 and 281 which com- I municate respectively through pipes 288 and 289 With pipes 86 and -85 leading to the ends of cylinder 31.

As shown in Figs. 2 and 11, the lever 282 has two locating positions to maintain the by-pass 5 valve pistons 216, 211 and218 in either of their correct operative positions. To accomplish this, the lever 282 is provided with an arm 290 which is limited in its angular movement by two studs 29| and 292 which are secured to a plate 293 afllxed to the machine base. The end of arm 290 is provided with a recessed portion 294 within which a plunger 295 is slidably mounted and constantly urged into engagement with the face of plate 293 by means of a spring 300. To assist l5 in locating the lever 282 in the correct angular positions, the end of plunger 295 which engages plate 293 is rounded and engageable with two recessed portionsv in the plate 293, as shown in Fig. 11. It will thus be seen that when lever 282 is shifted to position 282a. indicated by dotted lines, arm 284 will be moved to position 284a, and the pistons will be moved to the left to such a position that piston 211 closes the admission of fluid into exhaust pipe |96 and uncovers ports 286 and 281 whereby fluid is free to communicate through valve chamber 302 and pipes 289, 288, 85 and 86 with both ends of cylinder 31, as shown in Fig. 6. The table 25 may be manually traversed by any suitable mechanism which in the present instance may comprise a rack and pinion device (not shown) operated by a hand wheel 305 mounted on the front of the machine. The rack and pinion device may be of any suitable construction such as, for example, that shown in the patent to C. H. Norton No. 1,563,310.

When it is desired to stop the fluid pressure actuated movement of the table, it is simply necessary to shift lever 282 to position 282a, whereupon the fluid may flow from one end of cylinder 31 to the other through by-pass Valve chamber 302, and the exhaust of fluid through pipe |96 from the table cylinder is cut off by piston 211.

-At this time, the table may be manually traversed by turning hand wheel 305. Since uid may not exhaust from the system at this time,

and since fluid pressure to the table is not cut 011. there is no opportunity for iiuid to drain out of cylinder 31, leaving air pockets or low pressure areas therein, and a smooth operation of the table 5 25 is assured.

Having thus described my invention, what I claim asnew and desire to secure by Letters Patent is:

1. A machine tool comprising a reciprocable work table, a fluid pressure actuated motor arranged to reciprocate the table, a reversing valve arranged to direct said reciprocation, a piston within the motor having two opposed operative faces of equal pressure areas, means to apply balanced fluid pressures against the opposed piston faces at any time irrespective of the reversing valve position and prevent movement of the table when desired, and means to reduce one of said balanced pressures While maintaining the other and cause a traverse of the table.

2. A machine tool comprising a reciprocable work supporting table, a fluid pressure actuated motor operatively connected to reciprocate the 70 table, a piston within the motor having two opposed operative faces of equal pressure areas, a

fluid pressure source, and manually operable means to traverse the table at any time independently. of the motor while maintaining nor- 75 mal operating :duid pressures directed from the uid pressure system against both of the opposed piston faces.2 f(

3. A machine tool comprising a reciprocable work table, a fluid pressure system including a fluid pressure operated-motor connected to re- 5 ciprocate the table, means including a reverse valve to control the extent and direction of table movement, manually operable means to traverse A the table independently of the motor, and a separate manually operable device connected Within l0 the uid pressure system which maintains Ithe fluid under operating pressure in said system connected to the motor when the table is traversed manually.

4. A machine tool comprising a reciprocable l5 work table, a fluid pressure system including a fluid pressure operated motor connected to move the table, said motor having a cylinder and piston means in the cylinder, a control valve arranged to direct fluid flow under pressure to either side 20 of said piston means, manually operable table traverse mechanism, and a separate manually operable means for by-passing the fluid from one side of the piston means to the other at any time, irrespective of the position of said control valve. 25

5. A machine tool comprising a reciprocable Work table, a fluid pressure actuated motor arranged to reciprocate the table, a piston within the motor having two opposed operative faces of equal pressure areas, a reversing valve connected 30 to reverse the ilow of fluid under pressure tc and from said motor to cause a table reciprocation', and means operable at any time to direct balanced fluid pressures simultaneously to both of the opposed faces of the motor piston and cause 35 the table to be brought quickly to a smooth stop without affecting the position of the reversing valve.

6. A machine tool comprising a reciprocable work table, a fluid pressure Asystem including a 40 uid pressure operated motor connected to traverse the table, a reversing valve arranged to control the direction of uid flow to said motor and thereby regulate the direction of table movement, dogs adjustably positioned on the table, valve 45 controlling means engageable by said dogs `and connected with the reversing valve to stop the table movement when it reaches predetermined positions, manually operable mechanism ari ranged to traverse the table independently of the fluid motor, and a separate manually controlled device for by-passing the fluid under full operating pressure from one side of said motor to the other at any time so that the table may be manually traversed Without disconnecting the operating fluid pressure therefrom.

7. A machine tool comprising a 'reciprocable work table, a fluid pressure actuated motor operatively connected to reciprocate the table, a pump arranged to continuously supply fluid pressure to said motor, a reversing valve arranged to direct table reciprocation, manually operable mechanism independent 1,of said motor arranged to traverse the table, means to control the rate of table reciprocation, and means independent of the reversing valve whereby the table may be manually traversed at any time without disconnecting the flow of uid pressure to and from the table actuating motor.

8. A machine tool comprising a reciprocable work supporting table, a fluid pressure actuated reciprocatory motor connected to move the table, said motor having a piston therein, a reversing valve having ports communicating with the opposite sides of the piston in said motor and arranged to control the direction of motor movement, said reversing valve also having ports communicating respectively with a iiuid pressure source and an exhaust, pistons within the reversing valve which may be moved to cause fluid communication between the ports and produce a table movement in either direction, means to move the reversing valve pistons to such positions that a balanced fluid pressure may be simultaneously applied at both sides of the motor piston to stop the table movement Whenever desired and means independent of the reversing valve'to by-pass fluid at any time from one side of the motor piston to the other and stop table traverse without reducing normal operating fluid pressure within the motor.

r9. A machine tool comprising a reciprocable Work table, a uid pressure actuated motor operatively connected to reciprocate the' table, a reversing valve arranged to direct fluid pressure to the motor and cause a table reciprocation, means operated by the table movement to shift the reversing valve to a neutral position and stop the table traverse at` a predetermined position, a pilot valve arranged to operate the reversing valve, a lever operably connected with the pilot valve, adjustable means on the table engageable with said lever to cause a reversal of the/table actuating motor when the table has reached a predetermined position, a resilient connection between said lever and the pilot valve arranged to absorb any excessive movement of the lever and thereby prevent damaging of the pilot valve, means to manually traverse the table and a manually controllable device in the fluid pressure system independent of the reversing valve arranged to bypass uid from one side of the motor to the other so that the table may be manually traversed at any time irrespective of the position of the reversing-valve and without disconnecting normal operative fluid pressure from the n/iotor.

10. A machine tool comprising a base, a reciprocable table mounted thereon, a fluid pressure system to reciprocate said table including a cylinder which is xed to the table, a pair of spaced pistons within said cylinder, a pair of piston rods, one end of each being connected to a piston and the other end of each rod being xedly connected to said base to maintain the pistons a sumcient distance apart to take care of expansion of the rods, and means including a fluid pressure control valve to convey fluid to the cylinder chambers on opposite ends of the fluid pressure cylinder.

l1. A machine tool comprising a base, a reciprocable table mounted thereon, a :duid pressure system to reciprocate said table including a cylinder which is xed to the table, a pair ofspaced pistons within said cylinder, a pair of hollow piston rods, one end of each being connected' to a piston and the otherend of each rod being xedly connected to said bese to maintain the pistons a, sumcient distance apart to `taire care of expansion of the rods, and means including Aa uid pressure control valve to convey fluid through the piston rods to the cylinder chambers on opposite ends of the uid pressure cylinder. Y

12. A grinding machine having a work carriage and a grinding wheel base, a fluid motor for operating the work carriage, a valve controlling said motor, a throttle valve, a manually operable start-and-stop valve and a by-pass valve operable with said start-and-stop valve to allow fluid to pass around the throttle valve to permit manual traverse of the Work carriage, substantially as set forth.

- WALLACE H. WOOD. 

